Amplifying device



y 1935- K. STEIMEL ET AL I 2,006,969

AMPLIFYING DEVICE Filed Dec. 15, 1953 INVENTOR KARL 672-74161 A-RMSTKLOTZ ATTORNEY Patented July 2, 1935 UNITED STATES AMPLIFYING DEVICEKarl Steimel and Ernst Klotz, Berlin, Germany, assignors to TelefunkenGesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, acorporation of Germany Application December13, 1933, Serial No. 702,160

In Germany December 28, 1932 Claims.

An object of the present invention is to provide a vacuum tube amplifierhaving at least four grids and utilizing such an amplifier tube toamplify both radio and audio frequency os- 5 cillations.

A further object-of the invention is to control one of the grids of suchan amplifier by means of the modulation voltage developed in the platecircuit of a diode detector which is coupled to one of the grid circuitsof the radio frequency amplifier portion of the tube.

Other objects of the invention will become apparent to those skilled inthe art as the description thereof proceeds. For a better understandingof the invention, however, reference is made to the accompanying drawingin which the single figure'is a schematic circuit diagram of anarrangement embodying our invention.

In our application, Serial .Number 673,850 filed June 1, 1933, of whichthe present application is a continuation in part, we disclose a vacuumtube amplifier having four grids in which the radio frequency signalenergy is impressed on the grid near the cathode, the second grid servesas a screen grid, while the circuit of the third grid includes anoscillation circuit from which radio frequency voltage issupplied to thefourth grid or one nearest the plate. This arrangement provides on theone hand a feed-back connection and on the other hand, by suitablechoice of the coupling means and bias potential of the fourth gridbetween it and the plate, plate rectification takes place so that themodulation component is secured in the plate circuit.

In the present arrangement we prefer to impress the radio frequencyvoltage obtained in the circuit of the third grid on a distinct andindependent rectifier, such as a diode or plate rectifier or the likeand to impress the audio frequency voltage separated therefrom, aftercomplete or partial elimination of radio frequency currents, upon thefourth grid and ensure audio frequency amplification between this gridand the plate. The special advantage of this arrangement is that thevoltage impressed on the fourth grid may be determined or regulated atwill. On the contrary, a certain limitation exists in the circuitsdisclosed in the above mentioned application, in that the voltage at thefourth grid is utilized for rectification as well as for regeneration.

As shown in the drawing the antenna may be connected to the first gridcircuit by primary 5 and secondary coil 6 the latter being tuned to thedesired incoming signal frequency by variable condenser 1. The screengrid 2 is connected to a positive source of potential, while grid 3,which serves as the plate of the radio frequency amplifier portion ofthe tube, "is connected to any desired positive source'of potential suchas a battery 23 through primary 15 of a radio frequency transformerwhose secondary l6 may be tuned to the signal frequency by a variablecondenser E1. The ends of coil [6 are connected to the plate l9 andcathode 20 of a diode vacuum tube detector l8, a high resistance l3shunted by a by-pass condenser 2| being connected in circuit as shown.The modulation v0ltage of the incoming signal as developed acrossresistance [3 is impressed through condenser l0,

which has a low impedance to audio frequency currents, on the gridnearest the plate or anode P. A high resistance It provides a grid leakfor grid 4 and it may be given the desired bias by means of a batteryl2. The cathodes of the amplifier tube and detector tube may beconnected together by a lead 22, as shown. The

amplified audio frequency current of the plate circuit may be suppliedto the output terminals 9 through the audio transformer 14 whose primary8 is in the plate circuit.

Having described our invention what we claim and desire to secure byLetters Patent is:

1. In an amplifying device, the combination of a vacuum tube having acathode, a signal control grid, a second grid, a plate and an auxiliarygrid located between said plate and second grid, a circuit tuned to thesignal frequency connected between said signal control grid and cathode,a load circuit connected between said second grid and cathode, adetector coupled to said load circuit, means for impressing the detectedcurrent on said auxiliary grid and an output circuit connected to saidplate.

2. In an amplifying device, the combination of a vacuum tube having acathode, a signal control grid, a third grid, a screen grid locatedbetween said signal grid and said third grid, an anode, an auxiliarygrid, means for applying a positive potential to said screen grid,acircuit tunable to the signal frequency connected between said signalgrid and cathode, means for impressing modulated .radio frequency signalcurrents on said tunable circuit, a load circuit connected between saidthird grid and cathode, a detector coupled to said load circuit andconnections between said detector and said auxiliary grid arranged toimpress the detected currents thereon, and an output circuit connectedto said anode.

3. In an amplifying device, the combination of a vacuum tube having acathode, a signal control grid, a third grid, a screen grid positionedbetween said named grids, an anode, an auxiliary grid positioned betweensaid third grid and anode, means for maintaining said screen grid at aconstant positive potential, a circuit tunable to the signal frequencyconnected between said signal grid and cathode, means for impressingmodulated radio frequency currents on said tunable circuit, a loadcircuit including the primary of a radio frequency transformer connectedbetween said third grid and cathode, means for tuning the secondary ofsaid transformer to the signal frequency, a diode detector having itsplate connected to one end of said secondary coil, a high resistanceconnected between the other end of said secondary coil and the cathodeof said diode detector, a circuit connecting the last named end of saidsecondary coil to said auxiliary grid, and a circuit connected to theplate of said tube arranged to transfer the amplified audio frequencycurrents to a pair of output terminals.

former primary coil, means for tuning the secondary of said transformerto the signal frequency, a diode detector having its plate connected toone end of said secondary coil, a resistor connected between the otherend of said secondary coil and the cathode of said detector, a condenserhaving one side connected to the last named end of said secondary coiland its second side to said auxiliary grid and an output circuitconnected to the plate of said tube.

5. The combination defined in the preceding claim in which the seriesconnection of a source of bias voltage and resistor is connected betweenthe second side of said condenser and the cathode of said detector.

KARL STEIMEL. ERNST KLOTZ.

